Re: [BUG] vlan-aware bridge breaks vlan on another port on same gmac

[Vladimir Oltean]

Hi Frank,

On Fri, Jan 20, 2023 at 05:45:35PM +0100, Frank Wunderlich wrote:
> Hi,
> 
> noticed a bug while testing systemd, but it is reproducable with iproute2
> 
> tested on bananapi-r2 with kernel 5.15.80 and bananapi-r3 with kernel 6.2-rc1,
> both use mt7530 dsa driver but different configs (mt7530 vs. mt7531).
> have no other devices to test.
> 
> first create vlan on wan-port (wan and lan0 are dsa-user-ports on same gmac)
> 
> netif=wan
> ip link set $netif up
> ip link add link $netif name vlan110 type vlan id 110
> ip link set vlan110 up
> ip addr add 192.168.110.1/24 dev vlan110
> 
> vlan works now, other side pingable, vlan-tagged packets visible in tcpdump on both sides

VLAN 110 is a software VLAN, it is never committed to hardware in the
switch.

> now create the vlan-sware bridge (without vlan_filtering it works in my test)
> 
> BRIDGE=lanbr0
> ip link add name ${BRIDGE} type bridge vlan_filtering 1 vlan_default_pvid 1
> ip link set ${BRIDGE} up
> ip link set lan0 master ${BRIDGE}
> ip link set lan0 up
> 
> takes some time before it is applied and ping got lost
> 
> packets are received by other end but without vlan-tag

What happens in mt7530_port_vlan_filtering() is that the user port (lan0)
*and* the CPU port become VLAN aware. I guess it is the change on the
CPU port that affects the traffic to "wan". But I don't see yet why this
affects the traffic in the way you mention (the CPU port strips the tag
instead of dropping packets with VLAN 110).

I have 2 random things to suggest you try.

First is this